Several areas of investigation will be pursued during the upcoming grant period. These investigations are designed to validate existing models and hypotheses, and increase our predictive capability relating to PCB degradation and concurrent environmental consequences. The following task areas will be emphasized: Task 1. The toxicological impact of PCB and its metabolites on microbial populations and physiological activity will be investigated in detail. These studies will include both short and long term PCB stress. Task 2. Completed assessment of the mutagenic potential of PCB and its metabolites. Studies will include the synergistic effects of PCB, metabolites, and other agents. Task 3. A comparative assessment of PCB biodegradation potential in diverse aquatic environments, including chronically PCB contaminated habitats, will be undertaken. Task 4. Demonstration of the long term effects of PCB contamination on the structure of the microbial community and influences on biodegradation rates.